I do the climbing / mariner thing where you twist the coil in hand for every loop of the coil, so that there are no twists in the cord or rope.
I was told that the daisy chain method is storing cords was actually hard on the cord due to the tighter loops. I have no data and mentally filed it under the "might be true, might not be". Personally, I have never lost an extension cord due to a wire failure- cuts in the outer insulation, serial replacement of the ends, but never due to an internal wire break. YMMV...
All the best,
Peter